The present invention relates to a process and a device for discharging lignocellulose raw materials, especially wood chips, saw dust, annual plants or wood waste, from a digester and for conveying the raw material to a refiner.
It is known that in the digestion of lignocellulose raw materials, the digested material is conveyed by a discharge screw and under pressure, and by a further feed screw into a pressurized refiner.
Such devices are, for instance, known from GB 658 104. Here, in an intermediate conveyor screw, the wood chips are pressed and the hot cooking liquor is returned to the digester, in order to utilize the heat content. However, a considerable part of the cooking liquor and also foreign matters adhering to the wood chips are nevertheless conveyed into the refiner and subsequently, into the dryer.
For the purpose of the present application, all pipes, ducts, and devices connecting the digester and the refiner are subsumed under the term “connection device”.
In the refiner, lignocellulose raw materials, for instance, wood chips, are defiberized. This pulp is then transported to a dryer via a blow duct, and in the dryer, the fibers are dried to a residual moisture of approx. 10% b.d.
One disadvantage of this known process consists in the fact that due to the high amount of liquid adhering to the wood chips, a high dryer capacity is needed. Another problem consists in controlling the emissions created by drying.